This application also claims the benefit of Japanese Application No. 10-066200 which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a projection display apparatus having a polarized beam splitter for receiving a light from a light valve and analyzing a modulated light. More specifically, the present invention relates to an improvement on the polarized beam splitter.
2. Description of the Related Art
In Published Japanese Patent Registration No. 2599309, disclosed is a color projection display apparatus for separating a light from a light source into respective color lights of R, G and B by a color-separation optical system, making incident each of the color lights on a polarized beam splitter to be polarized and separated, making incident one of lights obtained by polarizing and separating a color light on a reflection light valve arranged for each color light to be modulated, making incident emitted reflected lights including the modulated lights on the polarized beam splitter, analyzing the same and thereby extracting the modulated lights, composing such analyzed modulated lights with one another by a composing optical system and then projecting the composed light by a projection optical system.
In FIG. 7, shown is a structure of the projection display apparatus disclosed in the Published Japanese Patent Registration No. 2599309.
Specifically, a light emitted from a light source 71 is made incident on a dichroic mirror 72 arranged as a xe2x80x9ccolor-separation optical systemxe2x80x9d on an optical axis. Then, the light is subjected to a color-separation into a B light to be transmitted and R and G lights to be reflected according to a dichroic characteristic of the mirror 72. The transmitted B light is made incident on a polarized beam splitter 74B for the B light as a xe2x80x9cpolarization and separation optical systemxe2x80x9d. An S polarized light of the B light reflected by a polarizing and separating section of the polarized beam splitter 74B is made incident on a reflection light valve 75B.
On the other hand, a mixed light of the reflected R and G lights is made incident on a dichroic mirror 73 arranged as a xe2x80x9ccolor-separation optical systemxe2x80x9d on the optical axis in parallel with the dichroic mirror 72. Then, the mixed light is subjected to a color-separation into a G light to be reflected and an R light to be transmitted according to a dichroic characteristic of the mirror 73.
The G light obtained by the color-separation is made incident on a polarized beam splitter 74G as a xe2x80x9cpolarization and separation optical systemxe2x80x9d. An S polarized light reflected by a polarizing and separating section of the polarized beam splitter 74G is made incident on a light valve 75G for the G light. Likewise, the R light is made incident on a polarized beam splitter 74R as a xe2x80x9cpolarization and separation optical systemxe2x80x9d. Then, an S polarized light reflected by a polarizing and separating section of the polarized beam splitter 74R is made incident on a light valve 75R for the R light.
The S polarized lights respectively made incident on the light valves 75B, 75G and 75R are modulated by signals applied to the same, reflected and emitted as lights including modulated and unmodulated lights. These lights are then made incident on the polarized beam splitters 74B, 74G and 74R for the respective colors, and subjected to an analysis by the polarizing and separating sections of the polarized beam splitters 74B, 74G and 74R. Only the modulated lights are extracted as P polarized lights transmitted through the polarized beam splitters 74B, 74G and 74R, and the analyzed lights are color-composed by a dichroic mirror 76 and a dichroic mirror 77 arranged as a xe2x80x9ccomposing optical systemxe2x80x9d. Then, a result of the color composing is projected to a projection lens 78 as a xe2x80x9cprojection optical systemxe2x80x9d.
In the projection display apparatus disclosed in the foregoing Published Patent Gazette, as described above, the dichroic mirrors 76 and 77 are used as the composing optical system. Another apparatus has also been disclosed, where a cross dichroic prism is used as xe2x80x9ccomposing optical systemxe2x80x9d.
The inventors of the present invention have investigated a significant problem inherent in the foregoing conventional projection display apparatus, which is constructed in a manner that the reflection light valves 75B, 75G and 75R are arranged for the respective colors, modulated lights among lights reflected by the light valves 75B, 75G and 75R are analyzed by the polarized beam splitters 74B, 74G and 74R arranged for the respective colors and then the analyzed lights are color-composed. Specifically, for an image projected on a screen by the projection optical system (projection lens 78), it was impossible to make registration adjustment (pixel positioning) coincident among the colors. Consequently, pixel deviation occurred.
Usually, with reference to the pixel positioning, relative to projected images from one of the light valves 75B, 75G and 75R for specified color lights, pixel deviation of specified positions of the other light valves 75B, 75G and 75R for the other colors must be limited to xc2xd pixel or lower, preferably within ⅓ pixel on full surfaces of the projected images.
A level of pixel deviation which is not a problem at all for the conventional light valves 75B, 75G and 75R, each of these having a pixel size of about 40 xcexcm, becomes a severe problem for a light valve having a very small pixel size of about 10 xcexcm.
Further, as a projected image is increased in size to be displayed on a large screen, the foregoing problem of pixel deviation will become more severe.
The inventors found as a result of extensive investigation that the problem of pixel deviation is not a problem that is created after execution of a vibration test or an environmental test such as a temperature cycle for the projection display apparatus. Rather, this is a basic problem which is created at the time of assembling the constituent members of the projection display apparatus. The inventors found a characteristic of the problem is that although an original shape of the display section of the light valve is rectangular, the display section is deformed to be a parallelogram, and consequently, pixel deviation occurs in a projected light from the light valve for a specified color light.
Furthermore, the inventors investigated projected images by replacing, among the constituent members of the projection display apparatus, the members for the respective light colors. When an experiment was made by replacing the polarized beam splitter with another for the other color light and arranging the same, a projected image of another color light was also projected in a parallelogram of the same size. Therefore, it was discovered that the projection of the image in the parallelogram rather than in the original rectangular shape can be attributed to the polarized beam splitter.
It is an object of the present invention to provide a projection display apparatus capable of reducing distortion of a projected light.
It is another object of the invention to provide a projection display apparatus for enabling registration of pixels of a plurality of light valves.
The present invention provides a projection display apparatus which comprises: a modulator including two-dimensionally arrayed pixel units for modulating an incident light and emitting the modulated light; an analyzer for analyzing the emitted light from the modulator; and a projection optical system for projecting the analyzed light from the analyzer. The analyzer includes a polarized beam splitter having a pair of prisms and an adhesive layer held between the pair of prisms. A difference in thickness between thin and thick portions of the adhesive layer is set equal to a predetermined value or lower based on a pixel pitch of the modulator.
According to the projection apparatus constructed in the foregoing manner, since a difference in thickness between the thin and thick portions of the adhesive layer is set equal to a specified value or lower based on the pixel pitch of the modulator, an occurrence of pixel deviation after passing through the polarized beam splitter can be prevented corresponding to an accuracy of the pixel pitch, and thus distortion of a projected image can be easily eliminated. Moreover, in the case of the projection display apparatus using the plurality of light valves, accurate pixel registration can be made for each light valve.
In accordance with a preferred aspect of the present invention, if a refractive index of the pair of prisms is n1, a refractive index of the adhesive layer is n2, a difference in thickness between the thin and thick portions of the adhesive layer is D and a pixel pitch is P, a value xcex94X is determined by the following expression       Δ    ⁢          xe2x80x83        ⁢    X    =      D    ⁢          xe2x80x83        ⁢          (                                    n            1                                2            ·                                                            n                  2                  2                                -                                  0.5                  ·                                      n                    1                    2                                                                                      -                  1                      2                              )      
and satisfies a following relationship:
xcex94X less than (xc2xd)P
With the projection display apparatus constructed in the foregoing manner, an occurrence of pixel deviation after passing through the polarized beam splitter can be prevented more effectively.
In accordance with a first aspect of the present invention, provided is a projection display apparatus which comprises: a light valve for modulating an incident light and emitting the modulated light; a polarized beam splitter for receiving a light emitted from the light valve and analyzing a modulated light as a light to be transmitted; and a projection optical system for projecting an analyzed light which has been transmitted through and emitted from the polarized beam splitter, wherein the polarized beam splitter has a structure where an adhesive layer exhibiting a refractive index n2 is held between two glass prisms, each of which exhibits a refractive index n1, and if a difference in thickness between thin and thick portions of the adhesive layer is D and a pixel pitch of the light valve is P, a value xcex94X satisfies a relationship of xcex94X less than (xc2xd)P, the value xcex94X being determined by the following expression:       Δ    ⁢          xe2x80x83        ⁢    X    =      D    ⁢          xe2x80x83        ⁢          (                                    n            1                                2            ·                                                            n                  2                  2                                -                                  0.5                  ·                                      n                    1                    2                                                                                      -                  1                      2                              )      
In accordance with a second aspect of the present invention, provided is a projection display apparatus which comprises: a light source; a color-separation optical system for color-separating a light emitted from the light source into R, G and B lights; polarization and separation optical systems arranged for respective color lights obtained by the color-separation of the color-separation optical system, each polarization and separation optical system performing a polarization and separation for a corresponding color light; light valves for the respective color lights, each of which has incident thereon a corresponding one of the polarized lights obtained by the polarization and separation of the corresponding polarization and separation optical system, modulates the corresponding color light, reflects and emits the modulated light; analyzing optical systems for the respective color lights, each of which has incident thereon a corresponding color light emitted from the corresponding light valve and analyzes the modulated light; a composing optical system for color-composing lights analyzed by the analyzing optical systems; and a projection optical system for projecting a light obtained by composing of the composing optical system, wherein the polarization and separation optical systems and the analyzing optical systems are polarized beam splitters arranged for the respective color lights, a polarized light reflected by each of the polarized beam splitters is made incident on the corresponding light valve, and among lights emitted from the light valves, a polarized light to be transmitted is used, and wherein each of the polarized beam splitters has a structure where an adhesive layer exhibiting a refractive index n2 is held between two glass prisms, each of which has a refractive index n1, and if a difference in thickness between thin and thick portions of the adhesive layer is D and a pixel pitch of the light valve is P, a value xcex94X satisfies a relationship of xcex94X less than (xc2xd)P, the value xcex94X being determined by the following expression:       Δ    ⁢          xe2x80x83        ⁢    X    =      D    ⁢          xe2x80x83        ⁢          (                                    n            1                                2            ·                                                            n                  2                  2                                -                                  0.5                  ·                                      n                    1                    2                                                                                      -                  1                      2                              )      
In accordance with a third aspect of the present invention, provided is a projection display apparatus which comprises: a light source; a polarization and separation optical system for polarizing and separating a light emitted from the light source; a color-separation optical system for color-separating one polarized light obtained by polarization and separation of the polarization and separation optical system in the foregoing polarization and separation optical system into R, G and B lights; light valves arranged for respective color lights, each of which makes incident each color light obtained by separation of the color-separation optical system, modulates the same based on a color signal and then emits the modulated light; a composing optical system for color-composing color lights emitted from the light valves; an analyzing optical system for extracting only a modulated light from a composed light obtained by the composing optical system; and a projection lens for projecting a light analyzed by the analyzing optical system, wherein the polarization and separation optical system and the analyzing optical system are polarized beam splitters arranged for respective color lights, a polarized light reflected by each of the polarized beam splitters is made incident on the corresponding light valve, and among lights emitted from the light valves, a polarized light to be transmitted is used as an analyzed light, and wherein each of the polarized beam splitters has a structure where an adhesive layer having a refractive index n2 is held between two glass prisms, each of which has a refractive index n1, and if a difference in thickness between thin and thick portions of the adhesive layer is D and a pixel pitch of the light valve is P, a value xcex94X satisfies a relationship of xcex94X less than (xc2xd)P, the value xcex94X being determined by the following expression:       Δ    ⁢          xe2x80x83        ⁢    X    =      D    ⁢          xe2x80x83        ⁢          (                                    n            1                                2            ·                                                            n                  2                  2                                -                                  0.5                  ·                                      n                    1                    2                                                                                      -                  1                      2                              )      